ANDROID: Streamline sched_domain_energy_f functions

There is no need to print that there is no sched group energy for a
sched domain.

It is e.g. perfectly fine to have an Energy Model on MC and DIE level
and not on SYS level.

The Energy Model consistency check between sched domains is done in
init_sched_groups_energy(). In case a sched domain level (l) has energy
data its child sched domain level (l-1) has to have energy data as well.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Change-Id: Iff1ecc86720a310f4b96282c3f41931aee733af2